Method of hot working heat-resistant metal articles



June 23, 1959 w. BETTERIDGE 2;89l,307

METHOD OF HOT WORKING HEAT-RESISTANT METAL ARTICLES Filed May 18, 1955 WALTER. BE TYTERIDGE INVENTOR.

ATTORNEY 2,891,307 Patented June 23, 1959 METHOD OF HOT WORKING HEAT-RESISTAN T METAL ARTICLES Walter Betteridge, Solihull, England, assignor to The International Nickel Company, Inc., New York, N.Y.,

a corporation of Delaware Application May 18, 1955, Serial No. 509,380 Claims priority, application Great Britain May 26, 1954 3 Claims. .(Cl. 29-423) The present invention relates to a method for producing hot-worked metal articles containing inner passages or cavities and, more particularly, to a special filler mate rial particularly adapted for the production of such "hollowed-out articles.

It is known that if one or more holes are made in a metallic body and filled with an appropriate material, and the body is then hot worked by extrusion or otherwise, the filler material will flow with the metal. If the filler can be removed by any process which does not affect the metal, the hot-worked body or sections cut from it will still contain holes after the removal of the filler, but the size and shape of these will depend on the change which has taken place in the external dimensions of the body and on the nature of the filler. Assuming that the filler behaves in exactly the same Way as the metal itself when subjected to deformation, it is possible to elongate the holes and reduce them changing their cross-sectional shape. This can be done, for instance, by extruding a billet or the like having a filled hole or holes extending parallel to the axis without changing the cross-sectional shape of the billet. If the cross-sectional shape of the billet or the like is changed, e.g., by hot rolling or forging between dies, the crosssectional shape of the filled holes will be changed in a way depending on the forces acting in the particular region of the billet or the like where they lie. In practice, when an axial hole has been made by removing a rod of metal, it is rare for the filler inserted in the hole to behave just as that rod would have done, and the extent to which the final cross-sectional shape of the hole resembles the cross-sectional shape which the rod of metal would have had depends on hot-working characteristics of the filler material.

By extrusion of the filled billet or the like through a die of a different shape and smaller cross-sectional area than the billet or the like, an elongated body can be produced in which the holes are elongated, reduced in cross sectional area, and also changed in shape.

If the size, shape and distribution of the final holes are to be uniform throughout a substantial proportion of the length of such an extruded product, it is essential that the extrusion be carried out under conditions of external lubrication and degree of reduction such that regular flow of the billet .or the like occurs, i.e. the phenomenon known to those skilled in the art as extrusion defect is avoided.

Provided that regular how is achieved, the final shape of the holes left after removing thewfiller material from an extruded billet willthus depend on:

(a) The hot-working-properties of filler and billet;

(b) The original shape of the holes;

(.0) The positions of the holes in :the billet cross sec- .tion; and.

.(d;) The change ,in cross-sectionaLshape of the billet on extrusion.

Processes of the :kind described may be used in the manufacture of lengths of metalwhich can be cut to form gas turbine blades or guide vanes. Such blades or vanes in cross-sectional area without.

attain very high temperatures in operation and may have to be cooled. One method of cooling them is to force air through passages in them and for this purpose, the passages may have to run from the root to the tip of the blade or vane, i.e., along its span. Such passages should be at predetermined points in the cross-section and may have to differ from one another in cross-sectional shape. Thus, blade or vane section in running lengths having one or more passages of very small cross-sectional area and predetermined shape, which cannot conveniently be made by machining, and possibly also with one or more passages of larger cross-sectional area for lightening purposes, may be made as follows:

A billet is provided with a number of axial holes and the holes are filled with a filler material. It is important that the holes should not extend right through the billet to the leading end, since otherwise some of the filler will squirt forwards during the extrusion and be lost. Next, the billet is raised to extrusion temperature, placed in the container of an extrusion press, and rotated so that the holes are correctly oriented with respect to a die of suitable section (preferably aerofoil section rather thicker than the desired final section). The billet is then extruded with external lubrication to ensure regular flow of the metal through the die. The extruded section still containing the filler is hot rolled through. shaped rolls to reduce the thickness and cut to lengths, and the filler is removed.

Extrusion of filled hollow billets can be also used in producing tubing of thin wall thickness and small diameter by direct extrusion from a hollow billet containing the filler. Such tubing is used for sheathing electric heating elements and is normally made by drawing a nickelchromium, nickel-chromium-iron or other alloy in from ten to fifteen drawing passes. By using a process of the kind in question, it is possible to produce the tubing in a single step of extrusion, though if very fine tubing is required it can be obtained by re-extrusion through asmaller die without removal of the filler. Other types of tubing may also be made by processes of the kind described.

Numerous materials which might be used as fillers are found to be unsatisfactory in practice when used with alloys which are difficult to work, particularly those alloys containing substantial amounts of nickel and chromium or nickel, chromium and cobalt which have good heatresisting and creep-resisting properties and are commonly used for gas turbine blades'and similar articles. For instance, graphite does not form coherent bodies which remain coherent and resistant to deformation during the plastic flow; copper is too soft and so does not maintain the desired shape and size of the cavities; alloy steels are difficult to remove owing to their inherent resistance to chemical or electro-chemical attack by media which do not cause simultaneous damage to the alloy of the blade or the like; glass is too readily deformed; and sand has too large a grain size, tends to form irregular holes, and has no tensile strength.

When the metal is a nickel-chromium or nickel-chromium-cobalt alloy, and especially when it contains one or more precipitable constituents such as titanium and aluminium, difficulty is experienced in finding a suitable filler. These alloys are very much more difiicult to deform than plain carbon steels even at the highest temperature at which it is permissible to operate. should have a corresponding stiffness at the high working temperatures. The ideal filler is itself a metal because The filler extruded section will contain no filler.

. and preferablyat least 50%.

otherwise the lines of the flow of the filler will not follow those of the surrounding metal. If the filler is more readily deformable than the metal, not only will the reduction in thecross=sec'tionalarea of a filler hole he proportionately greater than that of the metal over at least some of the length of the hole but also this area will vary along the length of the hole. The extent of these variations, measured for example as the deviation from the mean cross-sectional area, will increase with the deformability of the filler.

If the filler is less readily deformable than the metal, it will tend to act as a moving mandrel in the extrusion.

The filler will all pass through the die before extrusion of the metal is complete, and the trailing end of the Further, the cross-sectional area of the hole formed will be irregular.

I have found that a quantity I call the deformability factor must not exceed a certain figure for success. This 'fa'ctor is determined by taking a cylindrical billet 3% inches in diameter and 6 inches long and drilling in it I a central hole /1 inch in diameter to a depth of inches.

This hole is then filled and the filled billet is extruded under conditions ensuring regular flow with an extrusion ratio of 6.25:1 to yield a rectangular product 2% x /1 of an inch in section and between 30 and 33 inches long. The reduction of the cross-sectional area of both the metal and the filler after the extrusion are ascertained at the midpoint in the length of the filler in both the initial and the extruded material. If the ratio of thefiller area before the extrusion to the filler area after the hot-working is R1 and the similar ratio of the metal areas is R2,

' then the deformabilityfactor is Rl/R2. The deformability factor is thus a measure of the relative deformability of the filler and the metal under the conditions of extrusion. Since the deformabilities of metal and filler may vary at different rates with changing temperature, this factor may depend on the temperature of extrusion, which of course is chosen in accordance with the metal of the billet.

I have found that if the cross-sectional area of the filled hole is not to deviate at any point by more than 5% from its mean, the deformability factor should not be greater than 1.20. Beyond this there is a danger that very small holes will be completely closed at one or more 7 points along their length.

I have also surprisingly found that when the filler material isstiffer and less deformable than the metal of the billet under the extrusion conditions, the deformability factor falls little, if at all, below 1. However, the lengthover which the hole is of adequate uniformity in cross section is reduced and there is considerable waste,

since the sections that contain either no filler or filler of irregular shape and so must be discarded are long.

Therefore, in choosing a filler material, it is necessary not only to have regard to the deformability factor but also to a factor which Iv call the recovery factor. This is the proportion of the total length of the extruded product in which the extent of the deviation of the area of the hole from the mean area over that length is not more than 5%. 7

To be satisfactory, therefore, the filler used must be such that the deformability factor at the extrusion temperature is not much greater than unity and does not exceed 1.20 and the recovery factor must be at least 20% The filler must also be a coherent body, i.e., must have tensile as well as compres- 2 sive strength. Moreover, the filler must, of course, be

capable of being removed from the finished article by methods which are harmless to the metal, e.g., by selective chemical or electro-chemicalattack. a

It has now been discovered that a special metallic filler material can bee'mployed in the manufacture of hot- 4 control, over the dimensions of said passages or cavities and to provide smooth walls therein.

It is an object of the present invention to provide an improved filler material specially adapted for the production of hot-worked metal articles containing controllably disposed internal passages or cavities.

It is a further object of the present invention to provide a method of making an improved filler material specially adapted for the production of hot-worked metal articles containing controllably-disposed internal passages or cavities.

It is a further object of the present invention to provide an improved method for manufacturing hot-worked metal articles containing controllably-disposed and controllablydimensioned internal passages or cavities.

It is yet a further object of the present invention to provide an improved method for manufacturing extruded metal articles containing controllably-disposed and con trollably-dimensioned internal passages or cavities.

' Another object of the invention is to provide a filler material which can be employed to define holes or other internal cavities or passages in metal shapes while said shapes are being subjected to hot-working operations but which can readily be removed from the completed hotworked article to provide internal cavities or passages having smooth walls.

The following description is to be taken in conjunction with the accompanying drawing in which:

Figure 1 is a part-sectional view of a billet in accordance with the present invention; I

Fig. 2A shows the discard portion of the product resulting from the extrusion of the billet shown in Figure l; and

Fig. 2B shows the extruded portion of the product resulting from the extrusion of the billet shown in Figure 1.

The invention is based on the discovery that certain manganese-titanium steels have properties making them suitable for use with those heat-resistant and creepresistant alloys that are heated in use to 700 C. or above and contain at least 25% nickel plus chromium or nickel plus chromium plus cobalt. The temperatures at which these alloys are worked are necessarily high, and even at these temperatures the alloys are diflicult to; deform. Naturally, the particular composition of the steel for sat isfactory results varies with the alloy of the billet.

According to this invention, the filler consists of a manganese steel containing by weightfrom about 1% to about 10% titanium, in addition to from about 5% to about 20% manganese. The steel should not contain more than about 0.5% carbon and may contain usual minor constituents and impurities of manganese steel. In the normal course of manufacture the carbon content will not ordinarily fall below 0.05%. Steels within the invention which have been tested with good results include those containing about 10% manganese, about 2% to 5% titanium and up to-about 0.3%' carbon, e.g., about 0.05% to 0.25% carbon. It is important that the titanium content of the special manganese steel contemplated in accordance with the invention be maintained within the range of about 1% to about 10%. Thus, when the titanium content is less than about 1%, the steel is'too soft-even with the maximum manganese content. On the other hand, when' the titaniu'rn'content exceeds about 10%, the steelbecomestoo diflicult to leach out of the hot-worked product using practical mineral acid solutions. The manganese content in combination with the titanium content of the special steel contemplated in accordance with theinvention is likewise important to impart stiifness to the special steel. Manganese alone fails to give the necessary strength at high worked metal articles containing internal passages or cavities to produce improved results, including improved temperatures. If titanium were used alone, so much of it would be required as to produce a steel diflicult to leach by aqueo u's solutions of about 20% to 25% nitric acid with orwithout other mineral acids, e.g., with about'1 to 2.7% titanium, from about 0.8% to 1.8%

hydrochloric acid. Such solutions, when operated attemperatures from about 85 C. to the boiling pointthereof have been found to be. convenient for removing. the filler steel ofv the invention by leaching. Manganese should be maintained within the range of about 5% to about 20% because when the manganese content is less than about 5%, it is necessary to use so much titanium that the steel is rendered brittle and ditficult to form into desired filler shapes. When the manganese contentexceeds about 20%, the steel is diflicult to cast into sound ingots and to work to desired filler shape. Moreover, the strengthof the steel at elevated temperatures becomes inadequate. The carbon content, in conjunction with the special. titanium and manganese contents of the steel filler material contemplated in accordance with the invention, should not exceed about.0.5% because the steel then becomes, undesirably brittle and diflicult to work. This is believed due to the formation of hard titanium carbide. Carbon in amounts below about 0.5% can be used to adjust the stiffness of the special steel filler to that of the billet. The special manganese steel may contain up to about 10% of minor constituents and impurities without changing the basic and novel characteristics thereof. Thus, the special manganese steel may contain nickel in amounts up to about 5%, chromium up to about 3%, silicon up to about 1%, molybdenum up to about 1% and other minor constituents and impurities normally present in steels as a result of the raw materials and manufacturing processes used. The contents of these minor elements and impurities need to be restricted so as not to interferewith the ready removal of the special steel filler material from a hot-worked metal body containing the same.

The preferred manganese steel compositions. contemplated in accordance with the present invention contain about 2% to about 3% titanium, about 8% to about 12% manganese and not more than about 0.3 carbon. These preferred steels are easily workable and display deformability and recovery factors particularly appropriate tothe nickel-chromium and nickel-chromium-cobalt high temperature alloys referred to hereinbefore.

As an example, the composition range of some nickel alloys at present extensively used for jet engine turbine blading and the like is from about 18% to 21% chromium, from about 15 to 21% cobalt, from about 1.8% aluminum, from to 0.10% carbon, from 0 to about 1.0% manganese, from 0 to about 1.5% silicon, 0 to about iron, and the balance nickel, except for residual deoxidants, such as magnesium and calcium, and impurities. A filler for use with such alloys may contain about 10% manganese, about 2% titanium, and less than 0.27%, i.e., 0.3%, carbon, e.g., about 0.19% carbon, the balance being iron. It is found that this filler enables substantially uniform holes of small diameter to be extruded in long lengths of turbine blading as shown in the drawing. Billet 11 shown in Figure 1 contains filled holes 12 and ram guide holes 13. The productresulting from the partial extrusion of billet 11 is shown in Figs. 2A and 2B. Discard 14 in Fig. 2A is the portion not extruded. Airfoil section 15 in Fig. 2B is the extruded portion which contains substantially uniform small size holes 16. The filler can be readily removed after extrusion or other hot working by dissolving in a. nitric-hydrochloric acid mixture, which does not attack the nickel-chromium base alloy. This last characteristic is important, assa steel is useless as a filler if it is not possible to remove it in some such way, as it is impracticable to pull the filler material out of holes which may be only about-05 mm.

in diameter. When the aforementioned filler was used in working a billet made from an alloy having a composition within the foregoing range, the deformability factor was 1.0 and the recovery factor was about 62%. When the carbon content of the filler was reduced to 0.10%,

"6 the deformability factor rose factor fell to 55%.

If. the titanium content is increased, the capacity of the filler for being, cold drawn is decreased and at the same time, the deformability factor is increased. Thus, when used with the same alloy, a filler containing about 87% iron, 10% manganese, 3% titanium and 0.08% carbon gave a deformability factor of 1.11 and a recovery factor of 67%. Both factors were substantially the same when the titanium content of the filler was raised to 4% and then to 5% at the expense of the iron content.

Another alloy commonly used because of its creepresisting properties contains about 20% chromium, about 0.3% titanium, about 0.1% aluminum, about 0.1% carbon and the balance nickel. As an example, a billet of one such alloy was drilled with axial holes which were filled with a filler containing about 88% iron, about 10% manganese, about 2% titanium and about 0.08% carbon, and was then hot worked. The deformability factor was found to be 1.06 and the recovery factor 67%.

In another example, a billet of an alloy containing about 16% cobalt, about 0.1% carbon, about 2.8% titanium and. about 1.8% aluminum, the balance being nickel, is provided with axial holes. A filler containing about 88% iron, about 10% manganese, about 2% titanium and about 0.2% carbon is disposed in said holes and the resulting filled billet is hot worked to provide substantially uniform filled holes in the resulting hot-worked article. In a similar case, a similar filler material is found to be too soft when it contains only about 0.08% of carbon. In that case, a deformability factor of 1.18 is found but the deviation from the mean cross-sectional area of the resultingholes in the final hot-worked article is found to be more than 5% over the whole length.

In all'the examples given, the temperature of extrusion was 1180 C.

The special manganese steel filler compositions may be employed with advantage in producing hollow metal shapes from billets made of alloys normally extruded at about 1200 C., e.g., nickel-chromiumalloys, nickelchrornium-iron alloys and nickel-chromium-cobalt alloys, including alloys containing substantial amounts of elements, such as titanium and aluminum. The special manganese steel filler material can also be used in working billets of austenic. stainless steels or of cobalt-base heat-resisting alloys, all ofwhich have high strength at elevated temperatures and are therefore difiicult to hot work.

Those skilled in the art will appreciate that the present invention is applicable to the fabrication of numerous types. and shapes of articles containing controllably-disposed internal passages or cavities which will usually be elongated in section and will have smooth walls.

Thus, the present invention may be applied in the production of a hollow blade having a number of cooling passages inits wall by assembling concentric tubes into a tubular unit having longitudinal passages between the tubes, drawing down this unit so as to reduce its diameter whileretaining the passages, and deforming the unit into a hollow blade. The passages may be kept open during deformation by. inserting therein the filler contemplated in accordance with the present invention. The filler may be put in the passages before the initial drawing down but preferably some reduction of the diameter of the unit is effected first to consolidate the tubes into a unit. Next, the filler is put in the passages and then the deformation is effected by drawing untilthe unit if of desired diameter and wall thickness, and thereafter pressingor. otherwise converting the unit, or an appropri ate length out of it, to the cross-sectional shape required in the blade.

The tubular unit may be made from either two or three tubes. If three tubes are used, the outside and inside tubes. are plain and the middle tube is corrugated sinusoito 1.04 and the recovery rehab? dally or otherwise and is of such dimensions that it will make a push fit over the inside tube and in the outside tube. nn assagesyat then formed on ,both sides of the middle tube by the spaces between the corrugations.

All three tubes may be of the same heat-resisting alloy, e.g., a creep-resistant nickel-chromium alloy, but to improve the heat conductivity the middle tube may be of copper, or the outer surfaces of the inside and middle tubes may be copper plated to allow the three tubes to be brazed together in the unit.

If two tubes are used, the passages are formed by longitudinal indentations in the inner Wall of the outside tube or the outer wall of the inside tube or, preferably, by indentations in both those walls, the indentations in the one being brought into register with those in the other to form the passages.

During the deformation of the unit, whether it be composed of two tubes or three, the wall may be drawn down so that it tapers in thickness if a tapering blade section is required.

The filler material comprising thepresent invention may also be employed for the production 'of hollow turbine blades and other blades having an integral root and containing cooling passages in the walls thereof. When this process is carried out to produce a hollow blade, a hollow metal slug containing a plurality of longitudinal holes in the wall thereof filled with the filler material contemplated by the present invention is prepared and is then extruded from a container throughan opening having the cross-sectional shape required fora turbine blade. The extrusion is stopped whenenough metal has been forced through the opening to form the blade and while enough metal remains in the body cavity to form the root. The extruded product may then be pulled'out rearwardly from the die or a split die may be employed which can be openedto remove the product. The central hole or holes in the extruded blade may be held 'open'during extrusion, if desired, by means of an extrusion ram having one or more forward extensions or spigots corresponding in cross-section to the desired contour of the center hole or holes required in the hollow blade.

The filler material contemplated inaccordance with the present invention may also be employed in the production of turbine wheel discs containing passages or cavities at predetermined locations therein or even to the production of hollow discs. When this process is carried out, one or more holes are prepared in an extrusion billet and the filler contemplated in accordance 'with the present invention is inserted in the holes. The billet is then subjected to axial pressure to deform the billet in a die having an opening all around the bottom, said opening leading to an annular cavity so that the metal in the die flows radially through the opening into the annular cavity and becomes disc-shaped. The filler moves radially with the metal so that, in the resultant disc, the filler extends from the surface at the end through which the holes were made originally to points close to the outer cylindrical surface of the disc. In other words, the filler now lies in holes which run partially axially and partially radially. In this manner, cooling passages may be provided in a turbine rotor disc by which a cooling agent may flow to the roots of the blades of a gas turbine motor.

It is of course necessary that axial holes madein the original billet should lie at such a radial distance from the axis that they will be within the metal of the disc produced. It may be desirable to drill the holes so that they lie on the surface of a cone within the billet, the apex of the cone facing the ram used for the deformation, so that the filler in the holes :will more readily move radially when the axial pressure is applied.

Another way of making cooling passages in a gas turbine rotor is to drill axial holes from one end of the billet to the other, fill said holes with a filler material contemplated in accordance with the invention, and deform the billet by opposed rams acting on the two ends of the billet. .Then each filled, hole in the deformed billet will be substantiallyof U shape with two short lengths at right angles tothearms of the U, these lengths and the base .of the 1U being substantially parallel to the axis. The bases of the Usmust then be exposed as, for instance, by machining away the overlying metal.

A further way of making cooling passages is to drill radial holes in the middle of the billet to communicate with a single central hole, which may be made in the billet and filled, or may be made subsequently in the disc produced from the billet.

If the fillers do not move identically during the deformation, the resultant disc may be dynamically out of balance, i.e., its center of gravity may be slightly eccentric. This can be rectified by enlarging one or more of the holes in the disc after removal of the filler.

The invention may also be employed in producing rotor discs of light weight. In such a case a single large hole .may be made along the axis of the billet but not completely through it, and in the extrusion the filler within the hole will be converted into disc shape, the filler disc lying centrally within the metal disc. After the removal of the filler, the central hole leading to the cavity within the disc may be tapped to receive the end of the rotor shaft. Alternatively, the faces or each face of the disc may be recessed to receive a flanged shaft, which is bolted or welded in position. Again, a single large hole may be made completely through the billet, and two opposed rams may then be used to produce. a hollow disc with an opening at each face. a

It will be appreciated that when anyof the foregoing processes is carried out, the filler material contemplated in accordance with the present invention may readily be removed, .for example, by chemical or electrochemical means, without damage to the hot-Worked article. When the filler material is removed, passages are provided in the hot-worked articles which have smooth walls and which are. controllably disposed within the hot-worked article. c

In preparing billets of heat-resisting alloys for working to produce hollow metal articles through the use of the special filler material contemplated in accordance with the invention, the initial holes provided in the billets of heat-resisting alloy can be machined by electric spark erosion to provide blind cored holes of annular or other section and having a substantially concentric core therein. When this procedure is employed, the special manganese steel filler material can be made up beforehand as a hollow shape which substantially fits the holes prepared in the billets. This procedure is described in a patent application U'.S. Serial No. 503,343, filed April 22, 1955, in the name of Alexander Barbour Graham issued June 3, 1958, as Patent No. 2,836,884.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to 'without departing from the spirit and scope of the invention, as those'skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim: a

1. A process for the production of heat-resistant metal articles from heat-resistant metal which comprises providing a heat-resistant metal billet having at least 'one hole therein, filling said hole with a steel filler containing about 5% toabout 20% manganese, about 1% to about 10% titanium, up to about 0.5% carbon, with the balance essentially iron, said filler having a deformability factor with respect to said heat-resistant metal of about 1 to about 1.2 and being selectively soluble with respect to said heat-resistant metal, hot working the filled heat-resistant metal billet to provide a filled heat-resistant metal article blank and thereafter selectively dissolving said filler from said heat-resistant metal.

2. A process for the production of heat-resistant metal articles from heat-resistant metal which comprises providing a heat-resistant metal billet having at least one hole therein, filling said hole with a steel filler containing about 8% to about 12% manganese, about 2% to about 3% titanium, up to about 0.3% carbon, With the balance essentially iron, said filler having a deformability factor with respect to said heat-resistant metal of about 1 to about 1.2 and being selectively soluble with respect to said heat-resistant metal, hot Working the filled heat-re sistaut metal billet to provide a filled heat-resistant metal article blank and thereafter selectively dissolving said filler from said heat-resistant metal.

3. A process for the production of heat-resistant metal articles from heat-resistant metal which comprises providing a heat-resistant metal billet having at least one hole therein, filling said hole With a steel filler containing about 10% manganese, about 2% to about 5% titanium,

10 about 0.05% to about 0.25% essentially iron, with respect to about 1.2 and carbon, with the balance said filler having a deformability factor said heat-resistant metal of about 1 to being selectively soluble with respect to said heat-resistant metal, hot Working the filled heatresistant metal billet to provide a filled heat-resistant metal article blank and thereafter selectively dissolving said filler from said heat-resistant metal.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,891,307 June 23, 1959 Walter Betteridge It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

olumn 5, line 4'7, before "0.10% carbon," insert about column 6, line 10, after "raised" insert first line 45, for "austenic" read austenitic line 67, for "unit if" read m unit is Signed and sealed this 22nd day of March 1960.

(SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON Attesting ()fficer Commissioner of Patents 

1. A PROCESS FOR THE PRODUCTION OF HEAT-RESISTANT METAL ARTICLES FROM HEAT-RESISTANCE METAL WHICH COMPRISES PROVIDING A HEAT-RESISTANT METAL BILLET HAVING AT LEAST ONE HOLE THEREIN, FILLING SAID HOLE WITH A STEEL FILLER CONTAINING ABOUT 5% TO ABOUT 20% MANGANESE, ABOUT 1% TO ABOUT 10% TITANIUM, UP TO ABOUT 0.5% CARBON, WITH THE BALANCE ESSENTIALLY IRON, SAID FILLER HAVING A DEFORMABILITY FACTOR WITH RESPECT TO SAID HEAT-RESISTANT METAL OF ABOUT 1 TO ABOUT 1.2 AND BEING SELECTIVELY SOLUBLE WITH RESPECT TO SAID HEAT-RESISTANCE METAL, HOT WORKING THE FILLED HEAT-RESISTANT METAL BILLET TO PROVIDE A FILLED HEAT-RESISTANT METAL ARTICLE BLANK AND THEREAFTER SELECTIVELY DISSOLVING SIAD FILLER FROM SAID HEAT-RESISTANT METAL. 